Forming sheets or films by depositing fibrous materials in thin layers and creating bonds between the layered fibers is a known process. This process is typically used to make paper in a slurry (screening) method using water. Paper made in a slurry method typically has intertwined cellulose fibers derived from wood, for example, held together in part by a binder (a strengthening agent (starch glue, water-based resin)).
However, because the slurry method is a wet method, it requires a large amount of water, requires dewatering and drying after the paper is formed, and therefore requires a large amount of energy and time. The water must then be appropriately processed as waste water. Meeting the growing desire for reduced energy consumption and environmental protection has therefore become increasingly difficult. Equipment used in the slurry method also requires large-scale utilities to meet the water, electricity, and waste water treatment needs, and reducing the size of the equipment is difficult. Methods that require little to no water, referred to as dry methods, are therefore desired as an alternative to making paper by the slurry method.
PTL 1 describes recovered paper board obtained by layering a resin-impregnated sheet on a layered form acquired by dry defibration of recovered paper and mixing adhesive with the defibrated fibers, and then applying heat and pressure.